SYDNEY (AFP) - An Australian convert to Islam arrested in the Philippines for using the Internet to urge people to join "jihad" in Iraq and Syria was branded "a fraud" on Monday by Foreign Minister Julie Bishop.

Robert Edward Cerantonio, 29, who also goes by the name Musa Cerantonio, was detained in the central city of Cebu on Friday and will be deported to Australia, Philippine police said.

A report in The Australian newspaper last month described Cerantonio as a preacher and "one of (the Islamic State's) most influential propagandists", but Bishop belittled the Melbourne native.

"It seems that he is just a fraud, because he was saying that he was fighting in Syria and Iraq when all the time he was holed up in a flat in the Philippines," she told Sky News.